Luzia Cleide Rodrigues

Dispersal Ability Determines the Role of Environmental, Spatial and Temporal Drivers of Metacommunity Structure

Recently, community ecologists are focusing on the relative importance of local environmental factors and proxies to dispersal limitation to explain spatial variation in community structure. Albeit less explored, temporal processes may also be important in explaining species composition variation in metacommunities occupying dynamic systems. We aimed to evaluate the relative role of environmental, spatial and temporal variables on the metacommunity structure of different organism groups in the Upper Paraná River floodplain (Brazil). We used data on macrophytes, fish, benthic macroinvertebrates, zooplankton, periphyton, and phytoplankton collected in up to 36 habitats during a total of eight sampling campaigns over two years. According to variation partitioning results, the importance of predictors varied among biological groups. Spatial predictors were particularly important for organisms with comparatively lower dispersal ability, such as aquatic macrophytes and fish. On the other hand, environmental predictors were particularly important for organisms with high dispersal ability, such as microalgae, indicating the importance of species sorting processes in shaping the community structure of these organisms. The importance of watercourse distances increased when spatial variables were the main predictors of metacommunity structure. The contribution of temporal predictors was low. Our results emphasize the strength of a trait-based analysis and of better defining spatial variables. More importantly, they supported the view that “all-or- nothing” interpretations on the mechanisms structuring metacommunities are rather the exception than the rule.

Temporal fluctuations of the phytoplankton community of the Baía River, in the upper Paraná River floodplain, Mato Grosso do Sul, Brazil

Subsurface samples were taken monthly (March/1993 through February/1994) in the Baía River, a tributary of the right bank of the Paraná River (22° 43′ S and 53° 17′ W). We analyzed temporal changes in the phytoplankton community in relation to density, biomass, richness and species diversity, equitability, size structure, and dominance. We related these to regional climate and hydrology, and to the physical and chemical variables of the water column. We determined 119 taxa, wich were numerically dominated by the class Chlorophyceae with 37 taxa. The classes Cyanophyceae and Bacillariophyceae contributed the most abundant biomass and were responsible for the two peaks that were observed. The high water period was generally characterized by lower phytoplankton biomass, higher richness and species diversity, and higher density of nannoplanktonic species such as Monoraphidium tortile in March, and Cryptomonas brasiliensis in January. During low water, however, the highest values of phytoplankton biomass were recorded, with heterocytous cyanophytes dominating during the phase of greater stability of the water column, and filamentous diatoms during periods of mixing turbulence. The fluctuations observed indicate that the hydrosedimentological regime of the Paraná River, together with the climatological factors, constitute the main forcing functions acting on the Baía River phytoplankton.

Phytoplankton assemblages in a Brazilian subtropical cascading reservoir system

Variations in the structure and dynamics of a phytoplankton community were determined during two periods in 2001, along five cascading reservoirs of the Iguaçu River, Paraná State (Brazil). The vertical dynamics of the phytoplankton was related to underwater light availability and the water column-mixing regime. Correlations between physical and chemical variables and phytoplankton abundance were evaluated by Canonical Correspondence Analysis (CCA). No significant cascading effect throughout the serial reservoirs was obtained. Thus, the main factor affecting the structure of the phytoplankton assemblages of each reservoir was the hydrodynamic pattern. The instability of the water column during the winter favored the development of R-strategist species such as Aulacoseira granulata, Urosolenia longiseta and U. eriensis in most reservoirs. In the period of the highest hydraulic stability and temperature, the greatest contribution to biomass came from Cyanophyceae S-strategists such as Aphanocapsa sp.1, Anabaena planctonica and A. crassa. The phytoplanktonic associations recorded were important indicators of the environmental conditions of these reservoirs.

Interannual variability of phytoplankton in the main rivers of the Upper Paraná River floodplain, Brazil: influence of upstream reservoirs

The interannual variation of phytoplankton communities in the three main rivers of the Upper Paraná River floodplain is evaluated in relation to changes in the hydrosedimentological regime. These changes are a result of climatic variability and the formation of Porto Primavera Reservoir, located at the upper Paraná River. Phytoplankton species richness and density were investigated in rivers during a prior period (1993-1994) and eight years after reservoir impoundment (2000-2007). Multiple analyses were conducted to test the differences between these time periods in order to find predictor variables for phytoplankton attributes. A total of 454 phytoplanktonic taxa were found. The regression analysis revealed significant differences between periods. In the years following construction of the Porto Primavera dam, species richness was lower in the Paraná River and density was higher in the three rivers. In general, the algal density decreased from 2005 to 2007. Diatoms and cyanobacteria contributed significantly to the total density during the period from March 1993 to February 1994. The years 2000-2007 presented the lowest diatom contribution to species richness and the highest cyanobacteria contribution. From 2000 on, cryptomonads and cyanobacteria dominated. The interannual variability of phytoplankton was probably influenced by changes in hydrosedimentological regime due to climatic variations (La Niña and El Niño-Southern Oscillation events--ENSO) and the operational procedures associated with an upstream reservoirs. Studies on climatic variability and its effects on hydrosedimentological regimes of the Paraná, Baía and Ivinhema rivers and the biota therein are necessary to obtain subsidies for management, including decisions related to the operation of dams upstream and downstream of the study area, with the purpose of minimizing risks to the Environmental Protection Area.

Effects of hydrological regime and connectivity on the interannual variation in taxonomic similarity of periphytic algae.

The aim of this study was to analyze the effects of flood pulses (intensity) on the richness and composition of periphytic algae in lentic environments of the Upper Paraná River floodplain, over a six-year period. Other factors, such as connectivity of the environments with the main channel of the river and the availability of substrate for the periphyton, were also evaluated. For qualitative analyses, periphyton community was sampled from adult petioles of Eichhornia azurea Kunth taken from the littoral regions of the lakes studied. A total of 457 taxa of periphytic algae, distributed within 141 genera and 10 classes, were registered in the four environments. The greatest richness of periphytic algae was observed in connected floodplain lakes, especially in 2007 and during high water periods. In both connected and disconnected lakes, richness correlated positively with water levels of the Paraná River. Richness was also positively correlated with the number of taxa of aquatic macrophytes. The specific composition of periphytic algae differed between high and low water periods, and between connected and disconnected lakes. Therefore, among the considered variables, it is evident that flood pulse constitutes the principal force acting on periphytic algae communities of the floodplain, followed by the degree of connectivity and the presence of aquatic macrophytes.

Influence of reservoirs on phytoplankton dispersion and functional traits: a case study in the Upper Paraná River, Brazil

A confluence zone in the Upper Paraná River Floodplain was sampled to verify the influence of upstream reservoirs on the dispersion and colonisation of phytoplankton. We hypothesized that the dilutive effect and high discharge limit phytoplankton colonisation in the main stem and that the phytoplankton functional structure in floodplain lakes is influenced by upstream reservoirs. The recruitment of functional group (FG) M from Rosana Reservoir was evidenced with low establishment in the main stem and colonisation in the floodplain lake. The lower connectivity with the Paraná River during limnophase reflected in water column total mixing and dominance of the FGs C and P in floodplain lake and greater stability of the water column, with dominance of the FG H1 in a secondary channel. In the potamophase, the Paraná River negatively influenced the phytoplankton biovolume in the associated environments. In this period, FG P was dominant in the secondary channel and FG X2 in the floodplain lake. Our results emphasize that despite the contribution of inocula to the Parana River from the upstream inflow and from tributaries, the phytoplankton depletion was due to retention and seston sedimentation in the Porto Primavera Reservoir, high discharge and dilution in this confluence zone.

Functional diversity and adaptative strategies of planktonic and periphytic algae in isolated tropical floodplain lake

Functional diversity and adaptative strategies of planktonic and periphytic algae in isolated tropical floodplain lake. This study aimed to test the hypothesis that after a great magnitude and high duration of flood pulse in floodplain, functional diversity of phytoplankton and phycoperiphyton communities will be higher during high water. The strategies’ dynamics evaluated during high and low water periods consisted of size classes, life forms, and functional groups. For the phytoplankton, the adaptations to floating, and for phycoperiphyton, the intensity and structure for attachment to substrate were also analyzed. Functional diversity was calculated from functional dendrograms of species. Functional diversity, richness, and density of both communities presented the greatest values during the high waters. In the high waters, Cryptomonas marsonii Skuja was dominant in plankton and Pseudoanabaena skujae Claus in periphyton, while in the low water, Merismopedia tenuissima Lemm. was dominant in plankton and Fragilaria capucina Desm. was dominant in periphyton. Thus, the flood pulse promoted the dominance of free-floating species in plankton, during the high water, and of metaphytic species in periphyton. In the low water, we observed the dominance of species with higher surface/volume ratio in plankton, and strongly attached in periphyton. We concluded that, in isolated floodplain lake, possibly the flood pulse directs the functional diversity of phytoplankton and phycoperiphyton.

Extreme hydrological periods: effects on phytoplankton variability and persistence in a subtropical floodplain

The variability and persistence of species are appropriate measures of stability for communities that have large fluctuations in composition, such as phytoplankton. Our hypothesis was that phytoplankton species richness and abundance depend on the environmental variability arising from different phases of hydrological cycles, since changes in the limnophase and potamophase promote environmental fluctuations in the floodplain. A sub-basin of the Upper Paraná River was assessed between 2000 and 2001, a prolonged limnophase period, and 2010–2011, a period of conspicuous potamophase and limnophase. The phytoplankton community differed between these two periods. The lowest species richness with elevated values of abundance was recorded in 2000–2001, when 18 taxa indicators were verified. Lower variability and greater persistence of phytoplankton were recorded in 2000–2001, when the environmental variability was low. Therefore, the prolonged limnophase had a negative influence on species richness and influenced the pattern of dominant species persistence, thus, corroborating our hypothesis, indicating greater phytoplankton persistence in irregular hydrological cycles. Hydrological cycles with limnophase and potamophase periods present greater variability and less persistence of phytoplankton species richness and abundance.

Phytoplankton functional and morphological groups as indicators of environmental variability in a lateral channel of the Upper Paraná River floodplain

AIM: Models of phytoplankton functional classification based on functional (FGs) and morphological (MBFGs) traits can be an important tool in aquatic monitoring. In this long-term study on phytoplankton, the goal was to use these two approaches to explain the changes in this community in an active channel of the Upper Parana River floodplain, depending on the environmental conditions imposed by the hydrosedimentological regime. METHODS: Samples were taken between 2000 and 2013. RESULTS: 196 taxa were identified. Bacillariophyceae and Cyanobacteria showed higher contribution to biovolume. Were recorded 11 FGs (A, C, E, H1, J, Lo, M, MP, N, P and X1). The FGs C, Lo, M, MP, P and X1 were common to both periods. Already the FGs A, E, H1 and J occurred only in limnophase, while the FG N occurred only in potamophase. Were recorded seven MBFGs (I, II, III, IV, V, VI e VII). All seven MBFGs occurred in both hydrological periods, however the MBFGs III, VI and VII contributed with high biovolume values mainly in the limnophase. The FG P and MBFG VI were indicator of eutrophic status, while the FG M and MBFG VII were indicators of mesotrophic status. Only FGs reflected the environmental variability. CONCLUSION: The classification of phytoplankton in FGs and MBFGs represented an important tool for understanding of the behavior and dynamics of the species in relation to environmental conditions. However, the FGs appear to be more related to environmental variation this lotic channel than MBFGs. Probably this is related to the refinement of this classification, which reflected the changes in the community, in long-term scale, influenced by local and regional characteristics imposed by the hydrosedimentological regime of the Parana River.

Drivers of phytoplankton richness and diversity components in Neotropical floodplain lakes, from small to large spatial scales

Understanding the distribution patterns of species and how spatial and environmental factors drive the structure of communities is crucial to the preservation of biodiversity. We evaluate, during the low and high water periods, the phytoplankton diversity in lakes of four Brazilian floodplain systems (FPs): Amazon, Araguaia, Pantanal, and Paraná. We hypothesized that (i) species variation/replacement among floodplains (β2) is the predominant mechanism in shaping phytoplankton gamma diversity; (ii) the variation in phytoplankton taxonomic composition within each floodplain (β1) is mainly governed by local environmental conditions due to the high dispersal ability of phytoplankton at small spatial scales; and (iii) variation in the phytoplankton taxonomic composition among floodplains (β2) is mainly influenced by dispersal limitation. Variation partitioning was used to evaluate the influence of spatial and environmental factors on species richness. Higher γ diversity was found in the Araguaia and Amazon FPs. The high contribution of β2 (large scale) to γ diversity revealed the high degree of environmental heterogeneity in each floodplain. β1 (small scale) was more influenced by environmental variables, and β2 by both spatial and environmental factors. Our findings showed that γ diversity was explained by the interaction between the two factors, and that these processes influencing variation were scale dependent.